1. Field of the Invention
The present invention relates to a fiber optic vibration sensor, and more particularly to a fiber optic vibration sensor comprising a single grating.
2. Description of Related Art
A traditional mechanical vibration sensor is large in size and heavy in weight. Hence, there are disadvantages of a narrow range of frequency responses, low sensitivity and limited scope of applications.
Fiber optic sensors have advantages of being resistant to electromagnetic interference, water and erosion, and have further advantages of low transmission loss and high precision effect. Thus, the fiber optic vibration sensor is one of the means for solving the disadvantages of the above-mentioned mechanical vibration sensor.
Even so, the common fiber optic sensor for measuring various physical properties generally is subject to the configuration or design thereof, and so is unable to meet the requirements of being compact, lightweight and economic in manufacture. If the optic fiber sensors serve as the vibration sensors, the characteristics of high sensitivity and a wide range of frequency responses will be missing.
Another known fiber optic sensor fiber optic sensor having highly-stable intensity primarily adopts a pair of Bragg gratings for sandwiching a sensing region formed by removing part of the cladding layer of a common optical fiber and then evaporating or doping a medium capable of reacting with an ambient material. In this connection, the light reflected from the optical fiber grating will be altered as a result of change in the sensing region. This is useful for probating a mechanical or chemical-reactive environment, but definitely cannot be used as a vibration sensor.
Therefore, it is desirable to provide an improved fiber optic sensor to mitigate and/or obviate the aforementioned problems.